Hi All, 
There are currently two topics of high interest.  First Australia, then down below, oxalic acid pads.

The varroa invasion into Australia

I’ve been speaking on a daily basis with one of the two beekeepers whose operations are infested, as well as others in the industry.
So far, over 1000 of their colonies have been euthanized, with many more planned to be burned.  As you can imagine, this is very emotional for those beekeepers, who have also been prevented from selling their massive inventories of honey on hand.

The Department of Primary Industries appears to be doing a good job of “contact tracing”(epidemiological links) and so far, all detections have been linked to these two operations.  The key issue is to define the perimeter of how far mites have drifted from those infested colonies.  My own tracking of marked bees indicates that there is a considerable drift of bees from hive to hive to at least a half-mile, and some to a mile.  Not to mention that a bee carrying a mite can forage for several miles away from its hive, and perhaps bump into another uninfested bee on a flower.

The obvious questions are whether mites have gotten outside of the containment zone, or established in the feral population.  If they are still limited to a small zone, there’s a feasible chance of eradication.  The concern is that it is currently winter in Australia, and some of the infested hives had high enough mite counts that it’s obvious that they’ve had varroa since at least early last summer.  This would have allowed time for considerable drift, perhaps into the hobby sector in Newcastle.

Those of us who have lived through the invasions of tracheal and varroa mites understand the futility of eradication if a mite is already well-established.  The offspring of even a single female mite can relatively quickly spread throughout a continent, especially if aided by inadvertent human transportation.

For better detection screening, the DPI just received a large shipment of sticky boards from the U.S. (which I’ve made clear are more efficacious at detection than alcohol washes).  They are also working on getting registered colony treatments into the country.  I hung out the past few days with one supplier in North America, whose phone was ringing off the hook for requests by Australian beekeeping supply houses.

When I was asked several years ago by the Department for recommendations for their incursion plans, I made the point that if they were not willing to take strong actions — including using fipronil bait stations to kill feral colonies — that their chances of eradication would be zero.
Although I have only had indirect communication with the DPI during this incursion, I am encouraged that they are indeed preparing to perform such baiting.

The commercial beekeepers in the country are well aware that the possibility of complete eradication is slim, but it’s clear that the agency, based on the lack of detections outside the containment zone, feels that they still have a fighting chance.  

Since beekeepers will soon need to start moving colonies to pollinate the almond orchards, restrictions on movement will need to be put into place, to prevent the dispersion of varroa throughout the country.  We all know that it only takes a single beekeeper to screw it up for an entire continent, so let’s cross our fingers that none do!

Aussie beekeepers have enjoyed having their honey and beeswax being miticide free.  Suggestions have been made for treating all hives going to almond pollination with Apivar strips.  There is of course pushback since beekeepers don’t want residues in their hive products.  

A big question is whether the strain of mites in the incursion is resistant to any miticides, so tests are being performed.  If the introduced mites are “amitraz-naive” this might be a worthwhile consideration, since such treatment in my own amitraz-free operation can actually completely eliminate every mite from a colony.

If there are any Aussie beekeepers reading this, here are some suggestions:

  • Keep a cool head.   The DPI appears to be well informed and doing a good job.  I commend them for trying to act with transparency and keeping the public informed.  Beekeepers can help them by cooperating fully, especially since there will be agents unfamiliar with bees.
  • Since most Aussie beekeepers are completely unfamiliar with mites, they should view photos of mites in alcohol washes or on sticky boards, to train their eyes to recognize them.  They are difficult for the untrained eye to spot, and you don’t want to miss a single one!
  • Alcohol washes or sugar shakes of 300 bees can easily miss a low-level infestation.  An “accelerated” sticky board count, using formic acid, rapid-release amitraz, or even whole-colony sugar dusting, will have fewer false negatives.
  • Speaking as one who performs thousands of mite washes, the best recovery is with either high-proof alcohol (90%) or Dawn Ultra detergent (which we prefer, since it gives the best recovery, is inexpensive, and not flammable).  I highly recommend using Dawn over alcohol.  It requires very little agitation, so far less work on the beekeeper’s part.  Refer to the following
  • An Improved, But Not Yet Perfect, Varroa Mite Washer – Scientific Beekeeping
  • Refining the Mite Wash: Part 4 – Comparing the Release Agents – Scientific Beekeeping
  • Although the chance of eradication of this incursion is slim, it is still possible, and well worth making the effort.
  • Beekeepers who are required to have their colonies euthanized will be compensated and should consider the sacrifice to be a heroic effort to save their industry.  Australia will inevitably get infested by varroa, but the longer they can avoid it, the better for the beekeepers.  Let’s all root for success in this containment and eradication of this incursion!

Extended-release oxalic acid for varroa management

This method of application of oxalic acid is not yet approved by the EPA.  However, EPA does not require an Experimental Use Permit for a limited number of hives.  Check with your State Lead Agency.


Although oxalic acid is not as reactive as stronger mineral acids, it can still cause eye damage, and if left on the skin, tissue damage.  Always wear safety glasses and waterproof gloves during preparation, and be careful to avoid splashing. 
After preparation or application, wash your hands and equipment with soap and warm water to remove any acid residues, or better yet, neutralize any acid on hands, hive tools, or smoker with a solution of 10 heaping tablespoons of baking soda per gallon of water.

Dosage and delivery matrices

For the extended-release application of oxalic acid, it can be dissolved into glycerin and applied to the hive by either laying pads across the top bars (if applied between two brood chambers), or by hanging strips over the top bars, extending down into the interspaces between the frames.  The delivery strips or pads must be applied so that bees freely contact the surfaces.
Biodegradable cellulose matrices such as cardboard (chipboard), Swedish sponges, or cotton absorbent fabrics may be used.  For full efficacy, roughly 55 square inches of the delivery matrix must be used if applied across the top bars, or 100 square inches if hung between the frames.  The instructions below are for moisturizer-free Swedish sponges, which hold 100 g of 1:1 (weight to weight) solution of oxalic acid dihydrate to glycerin.  Other matrices, or different ratios of acid to glycerin, will require different preparation.


For extended-release application, oxalic acid can be dissolved in glycerin and absorbed into any number of absorbent matrices.  Field data suggest that for a double-deep hive, there should be roughly 60 square inches of the matrix, holding roughly 100 g of 1:1 OA:glycerin (weight to weight), although other ratios may be used (the higher the ratio of glycerin, the more rapidly the OA is dispersed upon the bees, sometimes with adverse effects).  For cardboard strips to be hung over the top bars, it will require more total surface area to hold the same amount of solution.
To prepare enough Swedish sponge pads to treat 10 full-sized colonies in double deep boxes:

  • First prepare the sponges by cutting them in half (into 3½” x 8” pads), each of which will absorb 50 grams of the solution (50 g oxalic acid dose per hive).
  • Wear safety glasses and waterproof gloves when preparing the solution.  Have a neutralizing solution of 10 heaping tablespoons of baking soda dissolved in 1 gallon of water on hand, to neutralize any spills.
  • Place 500g OA dihydrate into a stainless steel pan, then add 500g (400 mL) vegetable glycerin (add the glycerin second in order to avoid splashing of the solution).
  • Place the pan over low/medium heat (preferably using a double boiler), and heat the ingredients while closely monitoring the temperature, not to exceed 160°F (the acid crystals will dissolve at as low as 110°F, and start to bubble if the temperature exceeds 170°F).
  • Occasionally stir gently until the acid crystals are completely dissolved and the solution is completely clear. At that point, remove the pan from heat.
  • While the solution is still hot, either (A) add twenty (20) (3½” x 8”) absorbent cellulose pads (or fifty (50) 1.25” x 15” cardboard strips) on the edge of the pan and allow them to absorb the solution, or (B) place the pads into a separate plastic container and slowly and carefully pour the still-hot solution over them.  With either method, you may need to use tongs to carefully turn the pads over to obtain full absorption (which must take place before the solution cools).  Be careful to avoid splashing of the solution.
  • If all the solution does not absorb, the excess should be drained off before allowing the pads to completely cool. For easier handling, allow the pads to cool for at least a day before application.  The oxalic acid will recrystallize during this time, and make the pads easier to handle and apply, with no dripping of solution (under conditions of high humidity, the pads will absorb moisture and may not “dry out”).
  • The pads can be stored in a labeled sealed container for up to 2 months, by which time the cellulose will slowly start to degrade.


  • The optimal timing of this treatment in treatment rotation is to apply the pads into the brood chamber at the time of placement of the honey supers.  This treatment should only be used once while colonies are rearing brood, rotating with miticides with other modes of action, such as formic acid, thymol, amitraz, or fluvalinate.  An oxalic dribble or vaporization can then be used during the winter brood break.
  • Wear waterproof gloves.
  • Using gloved hands or tongs, apply two pads between the brood chambers, placed so as to be within the cluster (avoid placing under a top feeder where syrup may spill, or directly against pollen substitute).  Placement of the pads must allow for movement of the bees over both surfaces.  The pads or cardboard strips can also be hung over the top bars, inserting them spread between the two brood chambers.  For cardboard strips, 3-4 will be needed per brood chamber.
  • For optimal efficacy, the pads must remain in the hive for 60-75 days, or until most of the acid has been distributed.  After treatment, remove the pads, handling them carefully, since they will still contain acid.
  • After removal, place the spent pads into a plastic bag or container for transport, and you’re your hands, hive tool, and smoker with a neutralizing solution.
  • Dispose of the spent pads in a landfill, or compost them.

Randy Oliver

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